Comparative evaluation of dental pulp tests in pulpal status diagnostics / Evaluación comparativa de pruebas de pulpa dental en el diagnóstico del estado pulpar

Introduction: The purpose of this study was to evaluate the effectiveness and compare the accuracy of pulp tests in the diagnosis of teeth pulpal health. Material and Methods: Traumatized (n=71) and non-traumatized (n=71) teeth from 42 patients were evaluated. Each tooth underwent cold, heat, electric and oximetry tests, followed by radiographic examination and calculation of the sensitivity, specificity, PPV, NPV and accuracy. Results: Clinical and radiographic examination showed no alteration for the 71 teeth from the intact contralateral group. From the traumatized group, 29 teeth presented complete endodontic treatment, 17 presented periapical alterations that required endodontic treatment and 25 teeth did not present conclusive radiographic alteration. The cold test showed a significantly higher proportion of correct results, while the electric test showed a significantly lower proportion. The data showed higher accuracy for the cold, followed by oximeter and heat tests, while the electric test presented the lowest accuracy. Cold and oximeter tests proved superior over the electric and heat tests, while the electric test showed better parameters when diagnosing diseased pulp. Conclusion: Combining two pulp tests seems reasonable for improving the pulp diagnoses using both oximeter and cold or oximeter and heat tests to detect healthy pulp; or cold and electric tests to define diseased pulp.

Introducción: El propósito de este estudio fue evaluar la efectividad y comparar la precisión de las pruebas pulpares en el diagnóstico de la salud pulpar de los dientes. Material y Métodos: Se evaluaron dientes traumatizados (n=71) y no traumatizados (n=71) de 42 pacientes. Cada diente se sometió a pruebas de frío, calor, eléctricas y de oximetría, seguidas de examen radiográfico y cálculo de la sensibilidad, especificidad, VPP, VPN y precisión. Resultados: El examen clínico y radiográfico no mostró alteración en los 71 dientes del grupo contralateral intacto. Del grupo traumatizado, 29 dientes presentaron tratamiento endodóntico completo, 17 presentaron alteraciones peri-apicales que requirieron tratamiento endodóntico y 25 dientes no presentaron alteración radiográfica concluyente. La prueba en frío mostró una proporción significativamente mayor de resultados correctos, mientras que la prueba eléctrica mostró una proporción significativamente menor. Los datos mostraron mayor precisión para la prueba de frío, seguida de las pruebas de oxímetro y calor, mientras que la prueba eléctrica presentó la menor precisión. Las pruebas de frío y oxímetro demostraron ser superiores a las pruebas eléctricas y de calor, mientras que la prueba eléctrica mostró mejores parámetros al momento de diagnosticar pulpa enferma. Conclusión: La combinación de dos pruebas pulpares parece razonable para mejorar los diagnósticos pulpares utilizando tanto el oxímetro como las pruebas de frío u oxímetro y calor para detectar una pulpa sana; o pruebas de frío y eléctricas para definir pulpa enferma.

Comparative evaluation of 3 microbond strength tests using 4 adhesive systems: Mechanical, finite element, and failure analysis.

STATEMENT OF PROBLEM: Bond strength (BS) values from in vitro studies are useful when dentists are selecting an adhesive system, but there is no ideal measuring method. PURPOSE: The purpose of this in vitro study was to investigate the influence of the evaluation method in the BS between dentin and composite resin. MATERIAL AND METHODS: Molars with exposed superficial dentin (N=240) were divided into 3 groups according to the test: microtensile (µTBS), microshear (µSBS), and micropush-out (µPBS). Each one was subdivided into 4 groups according to the adhesive system: total etch, 3- and 2-step; and self-etch, 2- and 1-step). For the µPBS test, a conical cavity was prepared and restored with composite resin. An occlusal slice (1.5 mm in thickness) was obtained from each tooth. For the µSBS test, a composite resin cylinder (1 mm in diameter) was built on the dentin surface of each tooth. For the µTBS test, a 2-increment composite resin cylinder was built on the dentin surface, and beams with a sectional area of 0.5 mm2 were obtained. Each subgroup was divided into 2 (n=10) as the specimens were tested after 7 days and 1 year of water storage. The specimens were submitted to load, and the failure recorded in units of megapascals. Original BS values from the µTBS and µSBS tests were normalized for the area from µPBS specimens. Original and normalized results were submitted to a 3-way ANOVA (α=.05). The correlation among mechanical results, stress distribution, and failure pattern was investigated. RESULTS: Significant differences (P<.05) were found among the adhesive systems and methods within both the original and normalized data but not between the storage times (P>.05). Within the 7 days of storage, the original BS values from µTBS were significantly higher (P<.001) than those from µPBS and µSBS. After 1 year, µSBS presented significantly lower results (P<.001). However, after the normalization for area, the BS values of the µTBS and µPBS tests were similar, and both were higher (P<.001) than that of µSBS in both storage times. In the µSBS and µTBS specimens, cohesive and adhesive failures were observed, whereas µPBS presented 100% of adhesive failures. The failure modes were compatible with the stress distribution. CONCLUSIONS: The storage time did not affect the results, but differences were found among the adhesives and methods. For comparisons of bond strength from tests with different bonding areas, the normalization for area seemed essential. The microshear bond test should not be used for bond strength evaluation, and the microtensile test needs improvement to enable reliable results regarding stress concentration and failure mode. The micropush-out test may be considered more reliable than the microtensile in the bond strength investigation, as demonstrated by the uniform stress concentration and adhesive failure pattern.

Crown fracture: Failure load, stress distribution, and fractographic analysis.

STATEMENT OF PROBLEM: The outcomes from load-to-failure tests may not be applicable to clinical situations. PURPOSE: The purpose of this study was to critically evaluate the efficacy of load-to-failure tests in the investigation of the fracture load and pattern of metal-free crowns. MATERIAL AND METHODS: Four groups were formed from 128 bovine roots restored with metal posts, resin cores, and feldspathic, leucite, or lithium disilicate ceramic systems or polymer crowns. Each group was divided into 4 (n=8) according to the cement: zinc phosphate, self-adhesive resin, autopolymerizing resin, and glass ionomer. Mean fracture loads from compressive tests were submitted to ANOVA and Tukey HSD test. Finite element and fractographic analyses were performed and associated with the fracture load and pattern. RESULTS: Significantly higher fracture load values were obtained for the lithium disilicate ceramic, but finite element and fractographic analyses showed that the cement effect could not be determined. The finite element analysis showed the cement likely affected the fracture pattern, confirmed that stresses in the cements were little affected by the crown materials, and found that the stressed conditions were lowest in the lithium disilicate compared with other crowns for all cement combinations. The stressed conditions in the crowns depended more on the adhesive properties than on the elastic modulus of the cement materials. The level of the stressed condition in the crowns at the occlusal surface was about the same or higher than along their cement interface, consistent with the fractography, which indicated fractures starting at the load point. Higher stress levels in the crowns corresponded with a lower number of catastrophic fractures, and higher stresses in the cements seemed to reduce the number of catastrophic fracture patterns. The highest stressed conditions occurred along the occlusal surface for crown materials with a low elastic modulus or in combination with adhesive cements. CONCLUSIONS: The method used was not appropriate either for investigating the crowns' fracture load and pattern or for stating the role of the cements within the crown-cement-tooth interaction.

Influence of different post design and composition on stress distribution in maxillary central incisor: Finite element analysis.

BACKGROUND: Post design and material has very important effects on dentinal stress distribution since the post placement can create stresses that lead to root fracture. MATERIALS AND METHODS: In this study we use finite element analysis (FEA) to evaluate stress distribution on endodontically treated maxillary central incisors that have been restored with different prefabricated posts. Six models were generated from the image of anatomical plate: Four metallic posts (ParaPost XH, ParaPost XT, ParaPost XP, and Flexi-Flange) and one fiberglass post (ParaPost Fiber Lux). The sixth model was a control-a sound maxillary central incisor. We used CAD software and exported the models to ANSYS 9.0. All the materials and structures were considered elastic, isotropic, homogeneous, and linear except the fiberglass post which was considered orthotropic. The values for the mechanical properties were obtained by a review of the literature and the model was meshed with 8-node tetrahedral elements. A load of 2N was applied to the lingual surface at an angle of 135 degrees. RESULTS: The stress results were recorded by shear stress and von Mises criteria; it was observed that there was no difference for stress distribution among the titanium posts in the radicular portions and into posts. There was higher stress concentration on the coronary portion with the titanium posts than with the glass fiber post. It seems that the metallic posts' external configuration does not influence the stress distribution. CONCLUSION: Fiber posts show more homogeneous stress distribution than metallic posts. The post material seems to be more relevant for the stress distribution in endodontically treated teeth than the posts' external configuration.